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Related Concept Videos

Overview of Protein Sorting and Transport01:45

Overview of Protein Sorting and Transport

Eukaryotic cells have different membrane-bound organelles with distinct protein requirements. The process by which proteins are targeted to a specific organelle is called protein sorting.
Protein sorting can be of two types: signal-based sorting and vesicle-based trafficking. In signal-based sorting, specific amino acid sequences called sorting signals target proteins to the proper location inside the cell either via gated transport or by protein translocation.  In gated transport, folded...
Transcellular Transport of Solutes01:23

Transcellular Transport of Solutes

Transcellular transport of solutes is the movement of substances like monosaccharides and amino acids through polarized cells. This transport mechanism is primarily seen in epithelial and endothelial cells aided by membrane transport proteins such as channels and transporters. The tight junctions between these cells confine the membrane proteins to the two sides of the cell. The epithelial cells have distinct apical and basolateral domains. In contrast, the endothelial cells show the luminal...
Membrane Transporters01:31

Membrane Transporters

Transporters are essential membrane transport proteins with functions related to cell nutrition, homeostasis, communication, etc. Approximately 7% of all genes in the human genome code for transporters or transporter-related proteins.
Transporters are mainly composed of alpha-helices, built from bundles of ten or more helices traversing the plasma membrane. The solute-binding sites are located midway, where some of the helices are broken or distorted, making space for the binding site through...
The Significance of Membrane Transport01:44

The Significance of Membrane Transport

The transport of solutes across the cell membrane is essential for metabolic processes, like maintaining cell size and volume, generating the action potential, exchanging nutrients and gases, etc. Membrane transport can be either passive or active. It can be simple diffusion, facilitated, or mediated transport aided by transport proteins such as transporters and channels.
Transporters facilitate either an active or passive movement of solutes. They can allow a single-molecule transport down its...
Membrane Proteins01:30

Membrane Proteins

Plasma membranes have integral transmembrane proteins involved in facilitated transport. These proteins are collectively referred to as transport proteins, and they function as either channels for the material or as carriers themselves. Channel proteins have hydrophilic domains exposed to the intracellular and extracellular fluids and a hydrophilic channel through their core that provides a hydrated opening for solutes to pass through the membrane layers. Passage through the channel allows...
Carrier-Mediated Transport01:06

Carrier-Mediated Transport

Carrier-mediated transport is a pivotal process in drug absorption, particularly for lipid-insoluble drugs, and encompasses facilitated diffusion and active transport. Facilitated diffusion allows drugs to move along their concentration gradient without energy expenditure, while active transport utilizes ATP to drive drug movement against this gradient.
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...

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Related Experiment Video

Updated: Jul 13, 2026

Analyzing the Function of Small GTPases by Microinjection of Plasmids into Polarized Epithelial Cells
09:38

Analyzing the Function of Small GTPases by Microinjection of Plasmids into Polarized Epithelial Cells

Published on: May 31, 2011

Transport protein sorting in polarized epithelial cells.

Li Zhang1, Michael J Caplan

  • 1Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520-8026, USA.

Sheng Li Xue Bao : [Acta Physiologica Sinica]
|August 19, 2007
PubMed
Summary

Epithelial cells use a complex sorting system to direct membrane transport proteins to specific cell surface domains. This process is crucial for physiological functions and involves cellular signaling pathways and protein structural information.

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Methods to Study Epithelial Transport Protein Function and Expression in Native Intestine and Caco-2 Cells Grown in 3D
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Methods to Study Epithelial Transport Protein Function and Expression in Native Intestine and Caco-2 Cells Grown in 3D

Published on: March 16, 2017

Area of Science:

  • Cell Biology
  • Physiology
  • Biochemistry

Background:

  • Epithelial cells require polarized cell surface domains for physiological functions.
  • Proper cell function depends on the targeted distribution of membrane transport proteins and cell-cell junctional complexes.
  • Epithelial organization relies on a cellular sorting apparatus for protein targeting and regulation of paracellular permeability.

Purpose of the Study:

  • To elucidate the mechanisms by which epithelial cells achieve and maintain cell surface polarity.
  • To understand how newly synthesized transport proteins are targeted to specific plasma membrane domains.
  • To investigate the nature of information within transport proteins that dictates their functional residence and the protein-protein interactions involved.

Main Methods:

  • Investigating signaling cascades involved in the initial formation of the polarized state in epithelial cells.
  • Analyzing the role of cell-cell and cell-matrix contacts in epithelial cell orientation.
  • Examining the function of a specific kinase, also identified as a cellular energy sensor, within these signaling pathways.

Main Results:

  • Epithelial cell polarization is initiated through signaling cascades responding to cell-cell and cell-matrix contacts.
  • A kinase functioning as a cellular energy sensor is implicated as a component of these crucial signaling cascades.
  • Evidence suggests that both cellular machinery and intrinsic protein information contribute to protein localization.

Conclusions:

  • The precise targeting of membrane transport proteins to distinct cell surface domains is essential for epithelial cell function.
  • Signaling pathways, including those involving a specific kinase/energy sensor, play a critical role in establishing and maintaining epithelial polarity.
  • Further research into protein structure-function relationships and protein-protein interactions will enhance our understanding of epithelial organization.